Effects Of Atomic Oxygen On 1Cr18Ni9Ti Stainless Steel

The 1Cr18Ni9Ti stainless steel was exposed in the plasma and the atomic oxygen (AO) using an electron cyclotron resonance source and a RF microwave AO source to simulate the AO exposure in space environment. The mass loss, surface nano-hardness and trobological property of the exposed specimens were measured. Chemical composition, phase constitution, and morphology of the exposed surface were analyzed by means of XPS, XRD, SEM, and TEM. Other surface features subjected to AO exposure were also characterized to explore the AO erosion effect on 1Cr18Ni9Ti stainless steel and the corresponding mechanism as well by utilizing AFM and contact angle meters.The results show that, both the plasma and the atomic oxygen result in mass loss and surface hardening of 1Cr18Ni9Ti stainless steel in a certain level. The nano-hardness of the exposed surface is increased with increasing AO fluence. For an example, the nanohardness rises from the original 3.012GPa to 3.897GPa under the fluence of 1×10²¹ atom/cm². The amount of surface defect is found to be larger than that of the unexposed one during the starting stage of plastic deformation. However, the plasma and/or the oxygen have little influence on the nucleation and growth of cracks as well as the fracture progress. The results of tribological test indicate that, both the plasma and the oxygen induce a decrease of the maximum friction coefficient during the original stage of friction, and have little effect on wear mechanism.The XPS analysis shows that both the plasma plasma and the oxygen lead to an increase in O content in the surface layer of 1Cr18Ni9Ti stainless steel. The TEM analysis demonstrates that there are expanded stacking fault and martensite phase existing in austenitic microstructure after AO exposure. The above changes in the chemical composition and the microstructure the surface layer of 1Cr18Ni9Ti steel induce the hardening of the exposed surface. In addition, the plasma plasma and the RF oxygen also result in a decrease in contact angle and an increase in roughness. Under the fluence of 1×10²¹ atom/cm², AFM measurement results illustrates that the surface roughness shows a distinct increase.